At present, light emitting diodes (LEDs) are commonly used in televisions, PC display devices, digital cameras, mobile phones, lamps, various sized billboards, traffic lights, and automobile warning lamps, etc. In recent years, the LED industry in Taiwan grows rapidly and has become the world's second largest supplier, just second to Japan. Therefore, the LED industry is considered as a blooming industry with a large business opportunity that is going to succeed the flat panel industry.
The Taiwan's LED industry shows a high growth in recent years and is expected to have a total annual output value of 25.3 billion NT dollars and a global market share of 21% (only second to Japan's 47%) by 2004, that Taiwan is the world's second largest LED supplier. The reason for LEDs to have such a fast growing market mainly resides in two driving forces. Firstly, the LED is being employed as the backlight source of display device; and secondly, the LED is being used as the replacement of the traditional incandescent light bulb and fluorescent lamp in the general light source market. In the foregoing two fast-growing markets, the LED has advantages on environmental protection, power saving and outstanding color performance; wherein the ban on mercury usage issued in 2006 by the environmental protection laws and regulations of European Union is the primary factor for driving the growth of these markets.
The conventional LED dot matrix signal display product as disclosed in the U.S. Pat. No. 6,756,893 is an LED assembly having a plurality of traditional LED module surrounding an automobile light, such as the headlight, taillight and signal light, etc., so that the LED surrounding a main lamp is enabled while the main lamp is malfunctioned.
Further, an LED warning lamp disclosed in the U.S. Pat. No. 6,700,502 comprises a plurality of LED modules disposed on a reflector, in which the LED module is a combination of LEDs of different colors.
A backlit light source device of TFT-LCD is disclosed in the U.S. Pat. No. 6,608,614, that the backlight device employs a waveguide to synthesize and redirect the light emitted from an LED module to an LCD panel so as to achieve the function of a backlit panel.
Further, a backlit module disclosed in the U.S. Pat. No. 6,196,691 is accomplished by installing an LED on the thicker part of a wedge-shaped light guide and adding an optical grating to assist the dispersion of light source. However, such arrangement only gives very little effect and is not suitable for large flat panel display.
Further, an LED assembly of billboard disclosed in the R.O.C. Pat. No. 290159 is accomplished by aligning a plurality of LED boards, each having a plurality of LED modules arranged thereon, to define a display billboard, so that the display billboard can show the required patterns by way of different arranging order of the LED modules.
In view of the foregoing description, most of the LED applications have the following shortcomings:    (1) Since the traditional LED arrays applied in signal devices, such as traffic lights, taillights, large outdoor billboards, etc., cannot be installed closely with each other, therefore it is general for a signal display applying traditional LED arrays to have a plurality of dark area seen on the surface of the signal device that shows an image formed by a plurality of light-dots, and is not a smooth and evenly lighted surface.    (2) The LED array used in signal devices, such as the traffic lights, taillights, large outdoor electronic billboards, etc., cannot achieve the smooth display effect under the prior-art structure. In addition, the LED array is not packaged by flat packaging, which increases the volume of the LED package and thus affects the smoothness of the image and text displayed on the signal device.